1. Field of the Invention
The present invention relates to a battery powered device incorporating a communication port, particularly although not exclusively a USB interface.
2. Description of the Prior Art
Customarily, hand held electronic devices such personal digital assistants (PDA), and cellular handsets have been powered by a rechargeable battery, the term battery being intended to encompass a collection of one or more cells. As a consequence, it is necessary for the user of such a device to recharge the battery regularly using a dedicated charger, always assuming a source of electrical power is publically available. Where a user possesses more than one such device and perhaps a laptop computer, it is necessary to carry a corresponding number of chargers. Typically, battery chargers are heavy, bulky and inconvenient to transport due to their trailing leads and connectors. Furthermore, where a user is traveling abroad, even should the charger prove compatible with the local electrical power supply, a power outlet adapter will almost certainly be necessary adding to expense and further inconveniencing the user.
It is thus an object of the present invention to overcome the disadvantages set out above and to further provide a device which permits a user to remove the need to carry a plurality of chargers and adapters when traveling. It is a still further object of the invention to permit the charging of a device in the absence of a locally available electrical supply.
Thus, according to one aspect of the present invention there is provided a battery powered device including a communications port and a charging circuit connectable to a battery, the charging circuit having a further connection to the communications port wherein the port, in use, provides power to the charging circuit.
Although the port may include a power line such as is found, for example, in a USB port, preferably the charging circuit obtains power from the data and/or control lines. Conveniently, the connection to the charging circuit is switched such that the controller or processor may make or break the connection in accordance with instructions received via a user interface of the device. Such instructions could arise from the detection of the onset of a communication over the data line in particular where this is a source of power. By disconnecting the charging circuit from the data line, the capacitance of the line is reduced and the data rate of the port is substantially maintained. It may also be appropriate to break the connection where an additional power supply is connected to a dedicated input to the charging circuit. By disconnecting the charging circuit from the port in such circumstances, the risk of over charging the battery is reduced. The device may also include means for providing data indicative of the status of a battery connected to the battery charger.
In accordance with a further aspect of the invention, there is provided a battery powered device including a communications port and a charging circuit connectable to a battery, the charging circuit being connected to at least one data and/or control line of said port, whereby power is received by said circuit during operation of said at least one line.
Particularly in the case of a so-called USB communications port, it is possible to deliver power to a battery charging circuit during communication activity between the device and a further device connected via suitable cabling thereto. Such communication activity may include the transfer of data and/or control signals. A switch may be provided to control the delivery of power to the charging circuit where the transmission conditions of the port dictate.
According to another aspect of the present invention, there is provided a method of charging a battery powered device containing a communications port, said device further including a charging circuit connectable to a battery, the method comprising connecting said charging circuit to at least one data and/or control line during delivery of data and/or control signals to said port whereby power is supplied from said at least one line to the charging circuit.